Roman Numeral Converter — Free Online Roman Numeral Tool

How to Use the Roman Numeral Converter

1. Choose the conversion direction: Use the radio buttons to select "Number to Roman" if you want to convert a regular number into Roman numerals, or "Roman to Number" if you have a Roman numeral and want to find its decimal value.
2. Enter your value: For decimal-to-Roman conversion, type any integer from 1 to 3,999. For Roman-to-decimal conversion, type using the standard Roman numeral letters: I, V, X, L, C, D, and M. The input automatically converts to uppercase.
3. Read the result instantly: The converted value appears in large text in the results panel. Below the main result, the converter shows the breakdown of how each Roman numeral symbol maps to its numerical value.
4. Check validation feedback: If you enter a non-standard Roman numeral (like IIII instead of IV), the converter still calculates the value but shows a note indicating the standard form. This helps you learn proper Roman numeral conventions.

The converter supports the full standard range from 1 (I) to 3,999 (MMMCMXCIX). It enforces the subtractive convention for output while being lenient with input, accepting both standard and additive forms for maximum flexibility.

Roman Numeral Conversion Rules

Symbol Values

• I (1): The basic unit. Can be subtracted from V and X. Maximum three consecutive I's allowed (III = 3).
• V (5): Never repeated, never subtracted from other numerals. Always stands alone or is preceded by I (as in IV = 4).
• X (10): Can be subtracted from L and C. Maximum three consecutive X's allowed (XXX = 30).
• L (50): Never repeated, never subtracted from other numerals. Similar role to V but at the tens level.
• C (100): Can be subtracted from D and M. Maximum three consecutive C's allowed (CCC = 300).
• D (500): Never repeated, never subtracted. The complement of M in the hundreds range.
• M (1,000): The largest standard symbol. Maximum three consecutive M's allowed (MMM = 3,000).

Step-by-Step Example

Convert 1,994 to Roman numerals:

1. Start with the largest value: 1,000 = M (remaining: 994)
2. Next largest: 900 = CM (remaining: 94)
3. Next: 90 = XC (remaining: 4)
4. Finally: 4 = IV (remaining: 0)
5. Combine all parts: MCMXCIV

Notice how 1994 uses three subtractive pairs (CM, XC, IV) for a compact representation. The year 1994 is a popular example because it uses all three subtractive pairs with different symbol levels.

Practical Examples

Example 1: Reading a Movie Copyright Year

Rachel notices the copyright at the end of a classic movie reads "MCMLXXXVIII" and wants to know the year. She types the Roman numeral into the converter:

• M = 1,000
• CM = 900
• LXXX = 80
• VIII = 8
• Total: 1,000 + 900 + 80 + 8 = 1,988

The movie was copyrighted in 1988. Film studios have traditionally used Roman numerals for copyright years in movie credits, a practice that continues in many productions today.

Example 2: Super Bowl Numbering

Carlos is looking up the Super Bowl and sees it referred to as "Super Bowl LIX." He converts LIX to find the number:

• L = 50
• IX = 9
• Total: 50 + 9 = 59

Super Bowl LIX is the 59th Super Bowl. The NFL has used Roman numerals for Super Bowl numbering since Super Bowl V (5), with the exception of Super Bowl 50 which used Arabic numerals as a one-time design choice.

Example 3: Building Cornerstone Date

Maria is studying architecture and sees "MDCCCLXXVI" engraved on a historic building's cornerstone. She uses the converter to find the construction year:

• M = 1,000
• DCCC = 800
• LXX = 70
• VI = 6
• Total: 1,000 + 800 + 70 + 6 = 1,876

The building was constructed in 1876, during the American centennial year. This example demonstrates how Roman numerals preserve dates in a timeless, formal manner that remains legible centuries later.

Example 4: Academic Outline Numbering

James is writing a research paper and needs to convert his outline numbering. He has sections numbered I through XII and wants to verify the values for cross-referencing. He converts each in the tool:

• I=1, II=2, III=3, IV=4, V=5, VI=6
• VII=7, VIII=8, IX=9, X=10, XI=11, XII=12

These small Roman numerals are commonly used in academic outlines, legal documents, table of contents, and footnotes. For converting numbers into their word form for formal writing, try our number to words converter.

Roman Numeral Reference Table

Tips and Complete Guide

Quick Conversion Strategy

The fastest way to convert a number to Roman numerals by hand is to decompose it into thousands, hundreds, tens, and ones, then convert each group independently. For 2,743: 2,000 = MM, 700 = DCC, 40 = XL, 3 = III, giving MMDCCXLIII. Memorize the key subtractive pairs (4=IV, 9=IX, 40=XL, 90=XC, 400=CD, 900=CM) and you can convert any number up to 3,999 quickly.

History of Roman Numerals

Roman numerals originated in ancient Rome around the 7th century BC. The system evolved from tally marks used by Etruscan shepherds. The original forms were purely additive (IIII for 4), and the subtractive convention was not standardized until the Middle Ages. Ancient Roman usage was inconsistent: inscriptions show both IV and IIII for 4. The system served the Roman Empire well for trade and record-keeping but was eventually supplemented by Hindu-Arabic numerals (0-9) which were introduced to Europe via Arab scholars around the 12th century.

Roman Numerals in Different Contexts

Different fields have slightly different conventions. Clock faces traditionally use IIII instead of IV (possibly for visual symmetry with VIII on the other side). Music theory uses Roman numerals for chord analysis (I, ii, iii, IV, V, vi, vii in a major key, where uppercase means major and lowercase means minor). Astronomy uses Roman numerals for naming moons (Titan is Saturn VI). Understanding these context-specific conventions helps avoid confusion when encountering Roman numerals in various disciplines. For number base conversions used in computing, try our base converter.

Common Mistakes to Avoid

• Writing IIII instead of IV: While seen on clock faces, the standard form for 4 is IV. Similarly, use IX for 9, not VIIII. Always use the subtractive form in formal writing and academic work.
• Invalid subtractive pairs: Only I can precede V and X, only X can precede L and C, and only C can precede D and M. Writing IC for 99 or XM for 990 is incorrect. The correct forms are XCIX and CMXC.
• Repeating V, L, or D: The symbols V (5), L (50), and D (500) are never repeated. VV is wrong for 10 (use X). LL is wrong for 100 (use C). DD is wrong for 1,000 (use M).
• Exceeding three repetitions: I, X, C, and M may be repeated at most three times. IIII, XXXX, CCCC, and MMMM are all non-standard. Use the appropriate subtractive form instead.
• Wrong order of symbols: Roman numerals must generally descend in value from left to right, except for the six specific subtractive pairs. Writing VX or LC is invalid because the subtractive rule does not apply to these combinations.

Frequently Asked Questions